As a technique relating to rewriting a data stored in an in-vehicle apparatus; JP-2005-332148A (corresponding to US 2005/0270888A) discloses a rewrite system for rewiring a stored data of an in-vehicle controller. In the rewrite system disclosed in JP-2005-332148A, when the rewrite apparatus is connected to a vehicle, the rewrite apparatus sends a rewrite data to the in-vehicle controller. In this way, the data stored in a non-volatile memory of the in-vehicle control unit is rewritten with the new rewrite data.
As a technique relating to rewriting a data stored in a non-volatile memory of a digital composite machine, JP-2007-310690 discloses a firmware update method. In JP-2007-310690, the non-volatile memory of the digital composite machine is divided into multiple sections, and multiple firmwares are allocated to and stored in the respective sections. When an external storage medium storing a new version firmware is connected to the digital composite machine, the digital composite machine compares, on a section-by-section basis, a version information of the present firmware with the version information of the firmware stored in the external storage medium. Then, the digital composite machine selects an update candidate firmware and informs an operator of the update candidate firmware. When the operator selects the firmware to be updated, the digital composite machine updates the section storing the selected firmware with the new version firmware corresponding to the presently-stored firmware.
In the update method disclosed in JP-2007-310690, since firmware update is performed to update-required part of the sections, an amount of time taken to rewrite a data can be shortened as compared with the case of JP-2005-332148A in which the data in all the storage areas is rewritten. In view of this, the inventor of the present application tried to apply the update method of JP-2007-310690 to a system which rewrites a data stored in an in-vehicle apparatus. However, the inventor of the present application encountered and found out the following difficulty.
In the update method of JP-2007-310690, the digital composite machine selects a section storing an update target firmware from among multiple sections. When this kind of configuration of selecting the update target firmware by comparing the version information of the present firmwares with the version information of the firmwares in the external storage medium is applied to the in-vehicle apparatus, it is unavoidable that the in-vehicle apparatus becomes complicated. Therefore, although the technique disclosed in JP-2007-310690 can shorten the amount of time taken to rewrite the data, it is difficult to apply this technique to a data rewrite system for a vehicle.